Four people impersonating police officials were arrested in central Johannesburg while allegedly demanding bribes from foreign nationals, claiming their passports were expired.

Police said the suspects, three woman and a man, aged between 27 and 45, were arrested on Friday morning.

"Two female suspects were arrested at corner Twist and Plein Street at 11:30. Police recovered two fake appointment police certificates," said police spokesperson, Captain Xoli Mbele.

"The other two suspects were apprehended at corner Noord and Wanderers Street at 11:45. They stopped three foreign nationals demanding passports."

Mbele said they "told one of the victims that his passport has expired and demanded three thousand rands". He added the pair was arrested while still demanding money from their alleged victims. 

"Police came to their rescue and apprehended the suspects. Police are on the ground to ensure that bogus police that are damaging the image of the police in the Johannesburg CBD are apprehended," Mbele said.

He said an investigation was underway and the suspects were expected to appear at the Johannesburg Magistrates Court on Monday.